The Lab Partner
by OnceUponASunday
Summary: Derek wondered why his blood boiled every time he saw his stepsister kissing Max. With a project and an experiment, he's determined to find out. CH 5 up!
1. The Project

THE PROJECT

Disclaimer: I don't own LWD but this whole story is purely mine.

Chapter 1: The Partner

At this moment Casey McDonald was not in much of a good mood. She was actually looking forward for the science experiment her teacher introduced a week ago; the Big Splash. She thought Emily would be her partner, yet at the D-day, swoosh, partner's gone. It turned out that Emily had chosen Sheldon over her. She remembered the conversation she had with her best friend not even 5 minutes ago:

"I'm really sorry Casey… Just for this once can I be Sheldon's partner?" Her best friend pleaded, "Pretty please? This is the only class that Sheldon and I are in together…" Casey wanted to say no but seeing Emily's look she sighed and nodded. "Fine. But you owe me Em." Looking at this reaction, Emily jumped at her best friend, hugging her. "Thanks Casey! This means a lot!"

At the mean time, however, she began to regret her decision. "Seriously..." Casey complained rather to herself, "Who am I supposed to partner up with _now_?" She skimmed the class. Just then she heard her stepbrother called her. "Hey Space-Case," he casually greeted, "Would you mind to kindly be my lab partner? Sam and Ralph ditched me."

"You must be kidding me…" Casey said under her breath. It was not that Derek was bad at science or anything… In fact, he was actually pretty good in science experiments when he put the effort. Playing in her mind however, is the torture and the pranks he would put on her later. She skimmed the class once again. And another time, just to make sure that there's no better option. The thoughts ran quickly in her brain: Max took Chem instead of Physics. Other capable candidates have formed their own pairs. Not having a partner is worse. And the last sentence she repeated over and over.

"Fine. But you have to follow some conditions;" Casey said finally, "one, we must equally contribute to the experiment. Two, you should not put pranks me, especially during the experiments. Three, we should plan together and create deadlines, four…." Casey kept on rambling until the teacher warned them of speaking too loud. Derek laughed and sat beside his stepsister. "See that Case?" Derek said slowly, pointing his finger at their friend, big mouth. He was known to be able to eat anything, and that when he speak he never really stops. At fourth grade everyone started to call him "big mouth" and at this point, no one even remember his full name anymore. "That's how much your mouth will expand next year if you don't stop yapping."

"De-rek!"

"Miss Mcdonald! As much as you are excited to have Mr. Venturi as your lab partner, you should keep voice down." Casey blushed at her teacher statement; embarrassed to saw that her friends' eyes were fixed on her.

'This experiment', Casey thought to herself sarcastically while covering her face with both of her hand in frustration, 'is going to be a blast.'

"I can't believe this Em… I have to endure a whole week of science class with Derek!" Casey said to her best friend while walking to their seats in the cafeteria. Putting down her tray, Emily replied "You know, some girls would die to change places with you." Casey put an obnoxious look on her face.

"I just didn't know what the girls see in him, ya know…" Casey said while eating her sandwich.

"Well. He's, you know, sort of cool." Emily told her as they watch Derek and his mates walk into the canteen. Casey somehow saw everything in slow motion. The two girls in the left were giggling while Derek greeted them, his groupies were excited as ever to see their idol and others just stared at him with admiration. "Oh I can't believe this." Casey rolled her eyes. She turned to her best friend, only seeing that Emily, who had a crush on him until not long ago, was still drowned in her admiration toward her step bother.

"Looks like I'm alone now…" the brunette said under her breath, sighing. Just then her boyfriend, Max put a tray beside her.

"Hey Case!" Max was wearing his usual football jersey. They were already going out for a month and even though there were ups and downs she enjoyed it. She started to explain what happened to her boyfriend and complain about the events that happened. Max listened to her, paying full attention to her face while eating his food when Derek came and mockingly told him, "I pity you Maxine… You have to endure this bird chipping for the rest of your life…" Sam, Ralph and Emily can't help but laughed at his statement. The trio walked away when they heard "De-rek!"

"I honestly can't believe him!" Casey said in an angry tone "I apologize for my stepbrother rudeness Max."

"Honestly Case, it's okay." Max replied. "I'm kind of jealous of your relationship with Derek you know… You seem to get along very well with each other" Casey eye widened "That's what you call GETTING ALONG? He was getting on my nerve every time we met! He is an obnoxious, sarcastic, ugly jerk!" Casey replied with such force that she hyperventilated.

"Calm down Case..." Max chuckled. "I wish I had a sister as cute as you to argue with. It looks fun" Casey blushed at his 'cute' statement.

Emily just watched as the lovey-dovey couple kissed briefly and blushed. "Oh get a room you guys…"

-ooooooooooooo-

From across the room Derek saw his stepsister kissing her boyfriend; he was somehow pissed at the scene. He didn't know why and he didn't know when this started to happen but his blood boiled every time he saw Casey kissing Max. He decided to keep them to himself since it was something he himself can't quite put his finger on.

**A/N: ** I just want you to know that I re-posted this chapter from my old account (also did some editing here and there). Wanted to continue it since... forever... but sadly I forgot which email I used for the account so now I ended up creating a whole new account, just to post the following chapters. Just so you know, this is DASEY. Thanks for reading. Do review :).

Next Chapter: The Design


	2. The Experiment Phase 1

Chapter 2:

THE EXPERIMENT phase 1

There was something different in her that made Derek longed for her. Different than anyone that he ever have known, she always have this dreamy eyes, naïve look on her face, and probably the fact that she actually was immune to his charm were the things that intrigued him. Derek scrolled the songs in his ipod, choosing the upbeat rap songs to take his mind off Casey. When his dad first introduced Nora and told him about the daughters she has he already dislike the idea of adding new family members, more so if he had known it comes with a new set of feeling for him as well.

Derek looked up at the ceiling and saw his calender. He was wondering what would it be like that day if Nora hadn't meet his dad but it just came to is mind that today he had to do double shift to fill in for someone else's shift. Derek looked at his watch. "Shit! ten to four already" jumping from his bed, he changed to the brown uniform and grab his car keys. 10 minutes was barely enough for him to drive to work.

He was glad that he made it in time. Throwing his bag and keys into his locker, he grab the usual working equipments, the brown pen and the notepad. "That was close Derek" Sally bumped her bag in his direction teasingly.

"Yes. That was." Derek replied. "But with this charm," he pointed to himself "I'm sure I wont be out of job even if I were"

They both looked at each other for a while and burst into laughter remembering, although silly, how true the statement was. Their last shift together some girls especially come to the place to eat just to talk to him and refused to order if Derek wasn't their server.

"Cocky brat, just do your job properly." The girl said to him before resuming her work.

"Yes Ma'am, will do." Derek chuckled and went out of the staff room. He smiled at how Sally thoughts really resembles his own. He wondered though whether Casey would react the way Sally did just now. When he realized that his thoughts were on Casey, again, he shook his head, trying to clear it out.

On the last hour of his shift, a group of jockeys went in. Derek immediately know who the bunch are from the red football jerseys he saw every single day in the cafeteria.

"Hey," he greeted the bunch, all of which have seated at one of the tables. "What you guys want to order?"

"Yo Derek! This your shift hour?" Derek squint his eyes and frowned. It was strange for him to dislike people, but Max was a special case. He especially don't like it when Max began to act friendly to him.

"Yes, and what would you like to order?" Derek had to put up a façade so not to show this annoyance. He was glad that Max didn't realize it and order instead. Once he was sure he got every order he left the group.

After a short while he put down some glasses of water and cannot help but hear their conversation. When he heard Casey's name, he froze. He left the scene but pretend to arrange nearby places so not to appear strange. Unlike the second Venturi, this particular Venturi basically despised the idea of eavesdropping but, this one he just could not miss.

"So when are you going to end that cover Max? You really are going to settle with the nerd?" Derek muscles subconsciously became tensed and his fists clenched. He could clearly hear the voice because of the little noise in the background. He was glad they come way past rush hours.

"Oh come on dude, I really like Casey" Derek respected Max for his answer but really his frown was getting deeper by the second.

"So it's not just for the homework?" The other asked before another jock continued, not letting Max answer properly "No, no, but I understand, under the neediness, she is a total babe…"

Derek jolted the moment he realize the touch of Sally's hand on his shoulder "You Okay D?" He then looked at his own hand and realized that he had bended one of the menus in his left hand.

"Uh, yeah, I'm fine" The boy answered hurriedly, fixing the menu so it wouldn't left a mark so bad. "Why wouldn't I be?" Derek asked in a manner that would fool most people but he saw the frown on Sally's face and know that she will not let this go so easily. He heard a 'ding' and realized the orders were ready. This was the first time he was happy that he had to send food to the customers.

When the last customer had gone home, Sally suddenly spoke. "You know I'm not going to let you go home before enough explanation right?"

Derek rolled his eyes and sighed. "It was nothing, really" Derek tried to convince his co-worker.

"Oh. So you were eavesdropping, folding one of our laminated menus into two, and frowning even when they gave you quite some tips because of nothing?" The blonde question sarcastically. "Not to be presumptuous but I know you D, and your pissed off face also." She let out a chuckle, still waiting for a response.

The boy sighed and wonder how many sighed he let out this last few days. "Honestly Sal, I don't really know why I'm pissed off. It's just that every time I see Max I just started to get this feeling inside of me."

"Every time you saw max, or every time you realized that Max was Casey's boyfriend?" Sally half interrupted him. When she saw he stayed quiet, she knew she was right.

"I don't know what's happening to me Sal." He shook his head. "And what's so funny?" He asked Sally who he heard chuckling her way when cleaning the table beside him.

"I didn't know you were this oblivious about your own feelings" She said between the laughter "The great Derek Venturi was blinded by his own feelings." Derek did not say a word but he didn't like where this conversation is going. "You like her Derek. That feeling just now toward Max is called jealousy."

He was right. Derek didn't like this one bit. He tried to object Sally but she couldn't stop smirking and Derek knew that she was up to no good.

"Tell you what, we'll do a bet. The next time you meet Casey and Max, have a lunch with them both. If you don't feel a jab every time he acted lovey-dovey with her, I'll treat you dinner or vice versa. But you have to be honest with me because it's your loss if I don't help you out."

"What you mean a jab?" Derek asked, pretty genuinely for a Derek.

"Oh. I can't believe this. You of all person who asked me out and kissed me before we even dated, who seem to be know it all about girls-"

"I know, I know, mock me all you want."

"Do you know that mocking you is fun?" Derek rolled his brown eyes at her statement. "Well, anyway, a jab, you know it when you'd hold your breath when you see them kiss, or feel pain when they're happy together, or something like that." At first Derek hasiteted. Really, he didn't need this stupid experiment to begin with, but he want to know how true Sally's statement was. He too wanted to know whether he like Casey in that way. Moreover, what can he lose whether or not he won? Probably 20 bucks for Sally's dinner, but that wasn't a very big deal for him. He'd treat Sally dinner anytime since she was one of his best friends after all.

A/N: Really this does not lead to any DerekxSally just to make it clear :P. Thanks for reading btw. Next chapter more on Derek and Casey. I hope this Derek is not OOC. Please comment for suggestion, recommendations, what you like, what you didn't like, or just anything :)

Next chapter: The experiment phase 2.


	3. The Experiment Phase 2

CHAPTER 3

THE EXPERIMENT phase 2.

A/N: Thank you for everyone who read and continued reading the story. Especially for the reviews :). Enjoy the chapter!

Monday morning physics were usually pretty boring. After last Friday design experiment approval though, Casey was looking forward to this class. Although throwing balls to a tank full of water and measuring the height of the splash wasn't exactly how you define 'fun', it was a lot more enjoyable than any other subjects for the day.

"Stop that grin Case, it's creeping me out" Her partner said to her while putting the tank of water onto the table in front of them. Without herself knowing, Casey had a grin from ear to ear all morning. True it was partly about the not-so-boring science experiment, but mostly was from the date he went with Max the day before. Given a rose with ribbons wrapped around it, going to the theatre and holding hands while watching a romantic movie together, and having dinner in a romantic place just the two of them was just enough to keep the happy mood for another day. She was treated like a princess, the perfect date night with Max.

On the real world however, Derek was pissed at the not-responding-still grinning-Casey. Derek dipped his hand into the water and removed it quickly, making some of the water drop to the table. He know he was going to have to clean it anyways so he didn't really care about the mess it would make, if he were to think correctly what will happen after this that is. He splashed the water to his stepsister and said "Stop daydreaming Space Case, if you don't land on the ground, your be stuck there forever."

Casey smile went off just like he expected. "De-rek!" she yelled, brushing off the small splashes of water from her face. Derek didn't just stop there however. His quick hand movement dipping in the water and waved it in the air added another splash of water to her face.

"If you do that one more time…" before she could finish her sentence, Derek splashed some more, laughing at her.

"You'll what? Soak me to the water?" Derek didn't really 'want' to tick her off, he just had to. On his defense though, she ticked him off first. Just like Derek predicted, Casey filled her now bowled hand with water from the tank and threw them to him. He dodged of course, moving to the left as the water came, just like he expected. What he did not expect was that their teacher was really behind him, receiving Casey's full comeback right at his face.

It didn't take a genius to figure out that the teacher was about to explode into big flames of anger. "Ms. McDonald, Mr. Venturi, " she began, taking deeper breath every sentence while wiping the water away from her face. "I think you both know that you crossed the line." Casey was apologizing for their behavior before the teacher finished her line, but Ms. Worrick just pulled her hand in the air right in front of her face, stopping Casey from apologizing any further.

"I won't accept your apology until you BOTH prove to me that you passed this project with a score higher than a B. I will, however, tolerate your behavior this one last time so that you could get some things done this period. Remember, failing this project means failing this class."

"Wait, wait," Now it was Derek's turn to say something. "Did you just raise the passing grade to be a B?" He said dumbfounded.

"I thought that brain of yours were both too smart for the class when you decided to play with water." The teacher sarcastically replied. She stopped for a while, waiting a comeback. Seeing none she continued, "seeing how you did in the class though Mr. Venturi, I'll be generous and extended it as far as B-." Casey and Derek knew that the teacher was angry and decided not to argue any further.

"Gee, thanks Klutz." Derek started sarcastically when they met for lunch. "Now I'd have to get at least a B- for physics"

"Hey, you started it!" Casey was already with Emily and Max, sitting in one of the tables.

"Mind if Sam and I sit here?"

"Course not" Emily said so fast that Casey's protest come to a waste. "Hey, I do mind" Casey tried to object but seeing Sam and Derek already sat in front of them Max calmed her down. "But Max, remember I told you about what happened today… it's all because of this stupid jerk!" She let it go, still with a frowning face.

"No wonder you have wrinkles already since you frown this much Klutz."

"Wha…" Casey subconsciously touched her forehead. "DE-REK!"

Derek chuckled, "Hey, truce, truce, at least for now. I'm trying to finish my lunch here"

"Yea it's alright Bun" suddenly Derek got Goosebumps hearing Max called Casey bunny. Names must be in the lists one of 'an ideal relationship'. "Sides, I'll still love you even if you do have wrinkles"

"Aw… that's so sweet Dear" Derek rolled his eyes at the conversation, regretting the money he spent for Sam's lunch to accompany him to sit in the seat they were sitting at the moment (without further explanation to why beside 'need to check something out'). Derek train of thoughts stopped when he saw her stepsister blushed because of Max's kiss. While Emily and Sam were busy talking about their English assignment, Derek watched the scene, almost thoughtfully. He saw how Max never let go of Casey's hand, how more often than not he'd pat her head. Every time Derek witnessed this small gestures of Max, he cringed and once in a while clenched his teeth. The fact that Max is a good person was good for Casey, he knew. But he cannot refute that he felt worse. By this time Derek already knew that he owe someone a dinner.

Sally was right after all; He was falling for his stepsister.

A/N: So how was it? I think I've spoiled you guys enough for the quick updates tho! But I'll say here first that it will be a while for a new update because I have to study for my summer finals by the end of this week X(. So do wait (and do review too).

Next chap: The Lecture


	4. The Lecture

Chapter 4: The Lecture

It all started when Derek was bored to hell with the guest speaker Ms. Worrick, yes, the Phsysics teacher, brought to class. Due to the schedule of her Physicist friend, the class ended up having an awkward introduction slash interview session about cosmic reaction between their experiment time slots, a topic they would learn later in the semester. Derek, being the usual him, pulled a prank on Casey. Although at first she tried to ignore him, she couldn't. From small pranks they progressed to throwing stationary at each other, starting with balled scraps of paper, and eventually erasers and similar stationary of their neighbor's.

The fuss they started in the class started to trigger other students to join in. Once half of the class started, it really was hard for the teacher to stop the fight. The physicist was pretty much fed up with his lecture being ignored and left the room, followed by Ms. Worrick's behind him, obviously apologizing till no end.

Not long after, Ms. Worrick came back to the class, enraged. She made everyone stayed in the class, writing a letter of apology to the Physicist for the whole lunch break after the period was over. As the bell rang, all of the students went out of the class, fed up with Ms. Worrick's yelling and words of disappointment. Casey and Derek, obviously the trigger of this havoc, were made to stay another half an hour, missing half a period of their other classes. Although Casey pleaded her teacher to stay back after school and go to humanities class for her daily quiz, Ms. Worrick stayed firm on her punishment. The physic teacher wouldn't let Casey and said it was her fault after all. For that half an hour after the break was over, Ms. Worrick gave them instructions to a 5 pages assignment about cosmic reaction due the day of the project assignment submission especially for the two.

"Really." Sighing, Derek finally broke the silence after the teacher left the two of them alone in the room. "This ought to destroy your straight A reputation, sis." The boy said rather jokingly.

"This isn't funny." Casey muttered, her face stoic of expression out of tiredness and disappointment toward herself. How could she fell this far into Derek's prank? Unlike her stepbrother, the brunette had to think about how she will finish everything right on time with As. After her brain was stuffed, she finally sighed, trying to look fine in front of his stepbrother. "At least one of us tried making things a hell better." Casey started, "so maybe you can be less of a jerk in front of me."

Derek looked at his companion's eyes. He let out a small groan. Please not the crying card. Derek ruffled his hair, feeling a bit guilty about starting the pranks at this housemate of his. He exhaled, not wanting to show that he actually cared.

"oh come on Casee... you know I was just joking!" Derek said. "We'd be fineee"

"Yeah, sure. _fine_." The other party replied, her voice cracking up. "How are we suppose to write a paper before even learning about what it was? Heck. I bet we can't even write a paragraph about it. Let alone a 5 page paper!"

"Don't you ever use google?" Derek made sure that Casey saw him rolling his eyes. He wanted to set the boundaries between him and his stepsister. Otherwise, she'd go even mushier with him and he would be tempted to give her a hug.

"Youtube. Yahoo. MSN. wikipedia?" Derek continued.

"Yes, yes," Casey finally stopped him from mocking her further. "I get you. We'll survive."

Casey gathered her books and prepared herself for another scolding from the class she should've been gone into about 45 minutes ago. She saw him glued at his seat, leaning even more comfortably to his chair.

"Not going to class?"

"Another 15 minutes and the class is over. It's barely enough to replace the lunch period I missed." Derek said rather oh-so-factly. He opened his eyes and straightened his back, locking eyes with his stepsister's.

"It will be all right princess. We'll pass." He said, smirking, catching her off guard. "After all you are one of the Venturies now."

**A/N:** This is a short one! Do you think Derek and Casey are a bit OOC? I hope not :S. Do review! :)


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